Many pump assemblies are known for dispensing flowable material such as hand soap. Previously known pump assemblies suffer the disadvantage that in operation of the pump, the flowable material being dispensed fills a discharge outlet and, after dispensing, may extend from the discharge outlet. This difficulty is particularly acute when the flowable material may have relatively high viscosity such as arises with hand creams and lotions and viscous toothpastes, skin creams and hand cleaners which may or may not include particulate matter.
The present inventors have appreciated that previously known dispensers do not provide advantageous arrangements for expelling from an outward most position of a discharge passageway leading to a discharge outlet substantially all of the flowable material.
The present inventors have appreciated that previously known piston pumps which attempt to inject air into a passageway to sever a fluid stream suffer from the disadvantages that the pumps are not operative when the piston of the pump is not be moved through a full stroke since the air is be injected merely if the piston is moved completely to either a retracted position or withdrawn positions. The present inventors have thus appreciated that previously known pumps suffer the disadvantage that they do not provide for adequate air severance insofar as a pump may be cycled through a partial stroke, that is, without actually moving completely to a withdrawn position and/or a retracted position.